Roadster 3.0

[dpeilow]

Tesla published the specs of the new pack on their blog update. They're claiming a 31% increase in capacity and about 70kWh for the pack, which is less than the current Model S cells would have delivered (let alone the new cells). I was hoping for newer chemistry too, but it's not the route they took.

Roadster 3.0 | Tesla Motors

How do we know they haven't gone with a higher energy density chemistry to lower the cell count and then just put "mass dummies" in the slots where the rest of the 6831 would have been? That might be a more cost effective way to lower overall cost.

 

[spaceballs]

How do we know they haven't gone with a higher energy density chemistry to lower the cell count and then just put "mass dummies" in the slots where the rest of the 6831 would have been? That might be a more cost effective way to lower overall cost.

Good point! I forgot about how they did that to the Model S packs.

 

[Doug_G]

How do we know they haven't gone with a higher energy density chemistry to lower the cell count and then just put "mass dummies" in the slots where the rest of the 6831 would have been? That might be a more cost effective way to lower overall cost.

They are going to build N of these upgrade packs, where N is <= 2,500. Suppose it takes $10 million to do the engineering - that's $4,000 per car at best, and potentially a lot more than that depending on N.

As for the actual value of N, a lot depends on the cost of the upgrade. If it is $15,000 then I would expect a large number of owners will upgrade. But even at that price many owners will think, "nah it's working fine now, I'll just run it until the battery starts to die." That means the upgrade could be delayed potentially many years. Plus there are a number of these cars sitting in collections not getting many miles.

If the cost is $40,000, then the upgrade numbers could be very weak. I certainly wouldn't bother upgrading my car at that price. My pack is down about 4% from brand new, and for longer trips I usually take the Model S.

Sure, there are many people who will want to get the upgrade as soon as it is released at almost any cost, but there are many more who will wait until they've "used up" their existing pack. Assuming a "reasonable" price for the upgrade, I'd say an optimistic projection would be 500 to 1000 upgrades the first year, and maybe 200 a year after that.

The above strongly suggests that they will go a route that minimizes the NRE cost. Simply swapping new cells into the existing architecture and tweaking the firmware is the lowest-cost route.

 

[djp]

How do we know they haven't gone with a higher energy density chemistry to lower the cell count and then just put "mass dummies" in the slots where the rest of the 6831 would have been? That might be a more cost effective way to lower overall cost.

Direct quote from the blog:

We have identified a new cell that has 31% more energy than the original Roadster cell.

The Model S cell has about 45% more energy than the Roadster cell, and the new Model S cell has about 55% more energy.

As Doug mentioned, the bulk of the cost of the new pack is R&D, not the cells. It would be more expensive to redesign the pack and BMS to use less cells than any savings in replacing cells with slugs. Also reducing the cell count would put more current draw on the remaining cells.

It's reasonable to take Tesla's explanation at face value. The simplest and cheapest upgrade path was to replace the Roadster cells one-for-one with cells that have 31% more capacity.

 

[bonnie]

My assumption regarding the rest of the upgrade (some body changes, from what we know, for increased aerodynamic efficiency) was that they were maxing out the battery possibility and doing whatever additional they could to meet Elon's initial 'about 400 miles of range' statement.

If they could use higher density cells or more cells, they would. That would be the easiest way to go. No way there are slugs in the new battery instead of maximizing the range - what would be the purpose? Could have saved them a lot of additional work.

 

[cswolfe]

Agreed.

I'm willing to shed a tear at the cost of a 3.0 upgrade, and expect to, but $40K would have to just say no. :/ We'll see. Fingers crossed.

 

[ecarfan]

I just hope that when Tesla announces the 3.0 upgrade is released and we can get on a list for having it installed, that the announcement also includes enough information to answer the obvious questions:
-- Is it possible to only purchase the 3.0 battery without the other 3.0 upgrade changes (body aero mods, wheel bearings, brake mods, different tires) and if so what is the price and what is the rated range at full charge without factoring in the range improvements from the other upgrade parts?
-- Can the 3.0 battery be treated similarly to the current Model S battery, that is can it be charged to full on an "as needed" basis and run down to a very low range value without excessive harm?
-- Does the 3.0 firmware range algorithm assume that all 3.0 mods are installed or can it calculate range only based on the 3.0 battery being installed and not the other mods?
-- Are the brake mods compatible with aftermarket pads like the Carbotech? (Tesla will likely give a generic answer something like "We do not support or endorse any aftermarket brake pads)
I am sure that others can think of more questions that Tesla should be able to answer as soon as 3.0 availability is announced.
It just seems to me that Tesla should answer all these questions at the 3.0 availability announcement so that we don't have to speculate or try to reconcile different answers from different Service Center personnel. I know, that's not the "Tesla Way", but it is time for Tesla to anticipate obvious questions and make public the answers at the new product announcement rather than have customers go round in circles trying to figure out what the answers are.

 

[dpeilow]

I'm still a bit confused why Tesla can't use larger capacity cells for this:

- I was under the impression that the Roadster's architecture was agnostic when it came to COTS 18650 cells of the same voltage etc.
- The COTS Panasonic 3400 mAh cell with the safety features needed for the Roadster (that they remove for the Model S) NCR18650B has been out a couple of years and is available at commodity pricing. The vaping and flashlight community has had them ages. The spread of prices for 3100 and 3400 mAh cells seems to be about the same.
- I am pretty sure if Tesla went to Panasonic and said can we also have 6 million of these please, they'd not be far off the Model S price.


What am I missing?

 

[JRP3]

Speculation: Possibly the NCA chemistry used in the S requires more aggressive temperature management than the Roadster can provide.

 

[GSP]

Good question David.

Here is more speculation, in addition to JRP3's possibility above:

Perhaps the NCA chemistry used in the NCR18650B is too aggressive for the Roadster pack design to pass all of the destructive UN shipping tests, like penetration or immersion in fuel fire. The Model S pack likely provides more protection for NCA cells.

GSP

 

[dpeilow]

Hmm, NCA is certainly no worse than LCO when it comes to safety and stability. It also has slightly better specific power. See Types of Lithium-ion Batteries – Battery University

I'm fairly sure its coming down to cost. I think they got a killer deal on some 2900 mAh cell.

 

[GSP]

I'm fairly sure its coming down to cost. I think they got a killer deal on some 2900 mAh cell.

That is a likely reason. Many owners will appricate a lower cost replacement when their first pack wears out, espically when the low cost path still has more range than the car had when new. The owners that want a cost-no-object, longest possible range, pack are probably a minority.

GSP

 

[dsm363]

If I could get over 200 miles at highway speeds in the cold that would be a win with this new pack. That's what I'm looking for.

 

[Jaff]

Agree David...that, and helping keep / increase the value of the unit in case the new Roadster is just too tempting to resist! :wink:

If I could get over 200 miles at highway speeds in the cold that would be a win with this new pack. That's what I'm looking for.

 

[supersnoop]

If I could get over 200 miles at highway speeds in the cold that would be a win with this new pack. That's what I'm looking for.

Define "highway speeds" and "cold." I'm in Texas, so highway speeds are 80 mph and cold is 50F. That said, I've done 200 miles at 60 mph at 33F.

 

[dsm363]

65-70mph in 30 degree weather.

 

[ecarfan]

I'm fairly sure its coming down to cost. I think they got a killer deal on some 2900 mAh cell.

If Tesla selected a cell type for the 3.0 battery upgrade that is reliable and stable but not the very latest design and got a good price on it I would be totally fine with that. Just give us a new 70kWh battery at an affordable price, please! I am anxiously awaiting the official announcement of pricing and release date so I can get on the wait list. The thought of getting a new and improved battery in my 2009 Roadster just a year after buying it is almost too good to be true.

 

[dpeilow]

I would be too. But I'd like to see a money no object, high margin option offered to demonstrate what is possible. I'm sure some owners will go for it.

 

[PokerBroker]

I'm looking forward to having my pack under some type of warranty again!!!

 

[richkae]

I am hoping the pack will be able to sustain higher output deeper into the rev range and give any kind of slight perf boost.
I want insane mode or ludicrous speed!
But I'd be happy with ridiculous speed or asinine mode.